Pump control system for suction dredges



July 25, 1950 Normal Mercury PUMP CONTROL SYSTEM FOR SUCTION DREDGES D. HOFER 2,516,386

Filed May 13, 1947 s REVERS/NG RELAY UNIT Level IN VEN TOR. .D. L JCofe 1" BY HTTYS Patented July 25, 1950 UNITED STATES PATENT OFFICE PUMP CONTROL SYSTEM FOR SUCTION DREDGES 7 Claims.

The present invention has for an object the provision of an automatic control system for suction dredges wherein the pump is driven by an electric motor; the control system being operative to maintain constant velocity in the discharge pipe, as is desirable for efficient operation of the dredge. This invention is a modification of the system shown in U. S. Patent No. 2,224,295 of December 10, 1940.

Another object of the invention is to provide a control system, for the purpose described, which is responsive to fluctuation in the speed of the pump drive motor; the system functioning to accelerate this motor when the velocity in the discharge pipe decreases below predetermined normal, and to decelerate the motor when the velocity is above said predetermined normal.

An additional object is to provide a pump control system, as in the preceding paragraphs, for a suction dredge wherein the pump drive motor of the dredge includes an electrically controlled speed regulator in its current supply circuit; said system including a dynamo driven from such motor, the output of the dynamo varying in proportion to the speed of the motor, and circuit means arranged so that the output of the dynamo actuates said speed regulator for the pump drive motor in a manner to control the latter in inverse relation.

A further object of the invention is to retain, in the present embodiment, the safety circuit arrangement of Patent No. 2,224,295 which locks the system, against functioning to increase motor speed, when velocity drop is due to plugging in the suction pipe; and to also retain the circuit means which reduces motor speed below normal if the plug is not promptly relieved.

It is also an object to incorporate, in the system of the present embodiment, another circuit arrangement designed to automatically accelerate the pump drive motor when plugging of the discharge pipe occurs whereby to clear said plug; plugging of the discharge pipe being normally evidenced by below normal velocity in the suction pipe rather than by substantial variance in pump drive motor speed, and said other circuit arrangement being responsive to such below normal velocity to cause such acceleration of the pump drive motor.

A further object of the invention is to provide a practical and eificient pump control system for suction dredges, and one which will be exceedingly effective for the purpose for which it is designed.

These objects are accomplished by means of such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claims.

The figure of the drawing is a diagrammatic illustration of the system and included circuits.

Referring now more particularly to the characters of reference on the drawings, the numeral l indicates the pump of a suction dredge; there being a suction pipe 2 leading to the intake of said pump, and a discharge pipe 3 to which the pump feeds. The pump is driven from a variable speed electric motor 4, through the medium of an endless drive 5.

Current is supplied to the motor 4 by means of a three-phase energizing circuit 6 having a speed regulator "I interposed therein, which speed regulator may be in'the form of a rheostat or the like.

The speed regulator l is adjustable to increase or decrease the speed of the motor 4 by means of 'a connected, reversible control motor 8.

The controlmotor 8 for the speed regulator I is connected to a reversing circuit 9 which is connected to the same source of supply as the energizing circuit 6; there being a reversing relay unit In interposed in the reversing circuit 9, for the selective control, in reverse directions of the motor 8. The reversing relay unit includes a speed increasing control circuit, indicated generally at Ii, and a speed decreasing control circuit, indicated generally at l2; the circuit II including a pair of wires !3 and i4, and the circuit l2 including a pair of wires l5 and I6. The circuits II and I2 are automatically and independently energized from a two-wire current supply circuit, including wires l'! and I 8, by means of the following automatic circuiting arrangement:

The variable speed electric motor 4 direct drives a D. C. dynamo I9, the output of which is delivered by an output circuit 20 directly to a contacting voltmeter 2! which includes a switch arm 22 and a pair of spaced contacts 23 and 24 between which the switch arm 22 is disposed; said switch arm being normally between said contacts without engaging either. This is the position of the switch arm 22 when the suction dredge is functioning normally, with the variable speed motor 4 turning at normal R. P. M.

When the speed of the motor 4 drops below normal, with the attendant drop in velocity in the discharge pipe 3, there is a consequent drop in the output of the dynamo l9, whereupon the switch arm 22 falls into engagement with the contact 23. When this occurs it closes the speed increasing control circuit 1 I, which in turn-acting through the reversing relay unit 1 ll-operates the control motor 8 in a direction to cause the speed regulator 'i to step up or accelerate the speed of motor 4. When the motor 4 again reaches its normal R. P. M. the contacting voltmeter 2! opens, breaking the speed increasing control circuit H.

The speed increasing control circuit 5 comprises the following:

The wire 13 leads from the reversing relay unit II] to the wire ll of the two-wire current supply circuit; there being a normally closed switch 25 of an opposed switch relay, indicated generally at 26, interposed in said wire I3. The wire M leads from the reversing relay unit ill to connection with the contact 23 of the contacting voltmeter Zl, and the switch arm 22 is connected by a wire 21 with the wire I8 of the two-wire current supply circuit. Through this arrangement, closing of switch arm 22 with contact 23 energizes the speed increasing control circuit '1 l, with the result previously explained.

As the motor 4 increases in speed beyond normal, with resultant undesirable increase of velocity in the discharge pipe-3, the output of the dynamo is similarly increases, being transmitted by the -'output circuit 29 to the contacting voltmeter "2 I, which reacts by closing the switch arm 22 with contact 2'4. When this occurs the speed decreasing control circuit I2 is energized, causing the reversing relay'unit I!) "to actuate the control motor 8 in a direction such that the speed regulator l slows down the motor 4. When the motor returns to normal R. P. M. the contacting voitmeter 2 opens, with switch armZZ leaving contact 2'4, whereupon the speed decreasing control circuit 1 Z similarly opens and becomes negative.

The speed decreasing control circuit 12 is arranged to produce theabove result as follows:

The wire it leads'from the reversing relay unit Ill to wire ll of the two-wire current supply circuit, while the other wire 16 of the circuit '52 leads from the reversing relay unit It to the contact 2 i; therebeing a normally closed switch 28 of "-an opposed switch relay, indicated generally at 2 9, interposed in said 'wire 46. It is thusevident that when sw'itch arm 22 closes with contact 24, "the control circuit I2 is energized as switch arm T22 is connectedby wire '21 with wire l8 of the' two-wire current supply circuit.

The purpose of the opposed switch relays 2B and 29 will hereinafter be described; the coil '30 of the opposed switch relay 26 normally being deen'ergized so that the switch 25 is normally closed, while the opposed switch relay 29 is of a type wherein thecoil 3| is normally energized to maintain thesw'itch 28 normally closed.

If a plug-occurs in the suction pipe -2 the motor 4 will of course decrease inspeed, and unless some safety arrangement were provided, the above described automatic control system would immediately speed up the motor, with possible serious damage to the pump system of the --dredge.

To preclude such result the following safety arrangement is provided:

The numeral 32 represents a mercury type manometer including a 'tube'33 connected to the suction pipe 2 at one end, ancl'having a vertical column portion depending into the mercury at the other end. This vertical column portion of the tube 33 is'of dielectric materiaLand includes a contact 3 1 at a point some distanceabove the mercury. Anothercontactsli cn'the body of the manometer'is in contact with'the mercury therein. -The contact 34 is connected to the wire 18 of speed decreasing control circuit l2.

4 the two-wire supply circuit, and said wire l8 has the coil 30 of the opposed switch relay 26 interposed therein. The wire !l is connected to the contact 35.

When a plug occurs in the suction pipe 2, the mercury rises in the vertical column portion of the tube 33 of the manometer, thus closing a circuit between contacts 34 and 35, and consequently closing an energizing circuit for coil 3!). Upon energization of coil 33, switch 25 snaps open, breaking the speed increasing control circuit ll so that it cannot function to increase the speed of the motor 4 when plugging conditions exist in the suction pipe 2.

If the plugging condition does not promply relieve, it is further desirable that the speed of motor 3 be then reduced below normal, and this is accomplished as follows:

A normally open, pressure-drop responsive switch 36 is connected by a pipe 3'! with the discharge pipe 3, and said switch '33 is arranged so that if plugging conditions in suction pipe 2 continue, with resultant pressure drop in pipe 3, the switch '35 closes. When this occurs the speed decreasing control circuit I2 is energized so as to reduce the speed of the motor t. This is accomplished by the following circuiting:

One side of the normally open, pressure-drop responsive switch 36 is connected by a wire 38 whic'hleads to, and connects with, wire it of the speed decreasin control circuit 12; the other switch 39 of the opposed switch relay 23 then being closed-as the coil 30 remains energized at such time. The switch 39 is open under normal con- 'ditions.

The opposite side of the pressure-drop responsive switch is connected by a wire 30 with the wire 2! which leads back to the wire E8 of the two-wire current supply system; thus closing the long as plugging conditions exist in the suction pipe '2 and do not relieve, the described system is operativeautomatically-to prevent the circuit H from speeding up the motor 5, and thereafter closes thecircuit l2 to automatically decrease the speed of the motor l. When the plug in the suction pipe 12 relieves, the circuit of course returns to normal.

The pumpcontrol system, in its present embodiment, includes a further safety circuiting arrangement operative to speed up the motor 4, under working conditions, when the discharge pipe 3 tends to plug, or engages at the .discharge end with .a bank or the like. The evidence -of resisted flow through the discharge pipe 3 is a vacuum drop in the suction pipe 2, but usually the motor -4-under these conditionscontinues at substantially the .same speed so that the circuits 'H and I2 would otherwise be unaffected.

Upon vacuum drop in the suction pipe 2 by reason of flow resistance in the discharge pipe 3, the mercury .in the vertical column portion of tube 33, which normally rests at a level between contact .34 and a series of contacts M therebelow, falls below said contacts 4!. When this occurs the normally energized coil 3| of the opposed switch relay 29 is deenergized, whereupon the switch 28 opens and the opposed-switch l2 closes. Upon closing of switch 42, the speed-increasing control circuit l l is energized, irrespective of the fact that the contacting voltmeter 2i may be open, i. e. switch arm 22 in normal position. With energization of speed-increasing control circuit "ll, the motor 4 is speeded up until the Thus, as

flow-resistance in discharge pipe 3 is eliminated, so that the system can return to normal.

The circuit arrangement which makes possible the last described automatic control comprises a wire 43 which leads from a switch blade 44 engageable, selectively, with one of the contacts 41 on the vertical column of the tube 33. At its opposite end the wire 43 leads to one side of the coil 3 I, while another wire 45 leads from the other side of said coil 3! to the wire 21. Thus, a circuit is normally established between wires I! and I8, and the coil 3| through the contacts 35 and 4|, but when the mercury falls below the contacts 4!, the circuit breaks, and coil 3! is deenergized, causing switch 28 to open and switch 29 to close. Switch *29 is interposed in a wire 46 which leads betwen wire 21 and wire 54. Consequently when the switch 29 closes the speedincreasing control circuit H is energized to increase the speed of motor 4.

In summary of the above described pump control system for suction dredges, such system is operative, automatically:

1. To increase or decrease the speed of motor 4, as working conditions may require to main" tain normal R. P. M. of such motor, and normal velocity in discharge pipe 3.

2. To break the control circuit for (1) above when plugging conditions in the suction pipe occur.

3. To automatically decrease the speed of motor 4 after plugging conditions in suction pipe 2 do not promptly relieve; and

4. To speed up the motor 4, in the event of flow resistance to the discharge pipe 3, so as to reestablish normal velocity of the latter.

The described system provides an efiicient and practical means for the automatic control of the pumping system of suction dredges, and further provides safety controls against damage which might otherwise occur under abnormal working conditions.

From the foregoing description it will be readily seen that there has been produced such a device as substantially fulfills the objects of the invention as set forth herein.

While this specification sets forth in detail the present and prefered construction of the device, still in practice such deviations from such detail may be resorted to as do not form a departure from the spirit of the invention as defined by the appended claims.

Having thus described the invention, the following is claimed as new and useful, and upon which Letters Patent are desired:

1. In combination with a suction pump having a suction pipe and a discharge pipe, a variable speed power drive for the pump, instrumentalities arranged to increase or decrease the speed of the power drive in inverse relation and responsive to variation thereof so as to maintain a predetermined normal working speed, means responsive to excess vacuum in the suction pipe above a predetermined normal operative to lock said instrumentalities to an extent to prevent actuation thereof to increase the working speed of the power drive, and other means responsive to continued excess vacuum in the suction pipe operative to effect actuation of said instrumentalities to decrease the working speed of the power drive below its normal, but only after operation of such first named means.

2. In combination with a suction pump having a suction pipe and a discharge pipe, a variable speed power drive for the pump, instrumentalities arranged to increase or decrease the speed of the power drive in inverse relation and responsive to variation thereof so as to maintain a predetermined normal working speed, means responsive to excess vacuum in the suction pipe above a predetermined normal operative to lock said instrumentalities to an extent to prevent actuation thereof to increase the working speed of the power drive, other means responsive to continued excess vacuum in the suction pipe operative to eiTect actuation of said instrumentalities to decrease the working speed of the power drive below its normal, but only after operation of such first named means, and additional means responsive to below normal vacuum in the suction pipe operative to effect actuation of said instrumentalities to increase the working speed of the power drive above normal.

3. In combination with a suction pump having a suction pipe and a discharge pipe, a variable speed power drive for the pump, instrumentalities arranged to increase or decrease the speed of the power drive, means responsive to excess vacuum in the suction pipe above a predetermined normal operative to effect actuation of said instrumentalities to decrease the working speed of the power drive, and additional means responsive to a vacuum in the suction pipe below a predetermined normal operative to effect actuation of said instrumentalities to increase the working speed of said power drive.

4. In combination with a suction pump having a suction pipe and. a discharge pipe, a variable speed power drive for the pump, instrumentalities arranged to increase or decrease the speed of the power drive in inverse relation and responsive to variation thereof so as to maintain a predetermined normal working speed, and means responsive to a vacuum in the suction pipe below a predetermined normal, regardless of the then existent normal speed of the power drive, operative actuation of said instrumentalities to increase the working speed of the power drive above said normal.

5. In combination with a suction pump having a suction pipe and a discharge pipe, a variable speed electric motor driving the pump, a speed control circuit for the motor, said circuit including a motor accelerating sub-circuit and a motor decelerating sub-circuit, means responsive to deceleration or acceleration of the motor relative to a predetermined normal working speed operative to effect actuation of the accelerating subcircuit or decelerating sub-circuit, respectively, and other means responsive to excess vacuum in the suction pipe above a predetermined normal operative to lock said first named means to an extent to prevent the same from actuating the accelerating sub-circuit.

6. In. combination with a suction pump having a suction pipe and a discharge pipe, a variable speed electric motor driving the pump, a speed control circuit for the motor, said circuit including a motor accelerating sub-circuit and a motor decelerating sub-circuit, means responsive to deceleration or acceleration of the motor relative to a predetermined normal working speed operative to efiect actuation of the accelerating sub-circuit or decelerating sub-circuit, respectively, other means responsive to excess vacuum in the suction pipe above a predetermined normal operative to lock said first named means to an extent to prevent the same from actuating the accelerating sub-circuit, and further means responsive to continued excess vacuum in the suction pipe amaese operative to effect actuation of the decelerating sub nircuiit :by said .first :named means, but only after operation of said other means.

7.. In combination with a suction .pipe having a .suction pipe and a discharge pipe, a variable speed electric motor driving the pump, a speed control circuit for the motor, :said circuit includinga motor accelerating sub-circuit and a motor decelerating sub-circuit, means responsive to deceleration or acceleration of the motor relative to a predetermined normal Working speed operative to seiie'ct actuation .of the accelerating sub-circuitor decelerating sub-circuit, respectively, other means responsive :to excess vacuum in the suction pipe above a predetermined normal operative to lock said first named :means to an extent to prevent the :same from actuating the accelerating sub-circuit, further means responsive :to continued excess vacuum in the suction pipe operative to eifect actuation of the decelerating sub-circuit by said-first named means, :but only after opera- REFERENCES CIT-ED The following references are of record in'the file of this patent:

UNITED STATES PATENTS Number Name Date 779,623 Porter Jan. .10, .1905 1,836,992 Schade et a1 Dec. .15, 19.31 2,106,858 Snyder Feb. 1, 1938 2,224,295 Hofer Dec. 10, 194:0 

